Processes for the oxidation of organic compounds such as hydrocarbons in the presence or absence of catalysts are well known. There is continuing applied research activity devoted to achieving economically feasible oxidation processes for commercial scale operation.
U.S. Pat. No. 3,282,994 describes a method for the oxidation of butane in liquid phase. U.S. Pat. No. 3,607,925 provides a process for the production of acetic acid by oxidation of butene-2 with nitric acid in the presence of a vanadium catalyst. U.S. Pat. No. 3,644,512 discloses a process for converting butane to acetic acid in liquid phase in the presence of a soluble cobalt compound.
Processes for the oxidation of hydrocarbons in the vapor phase by means of oxygen-containing gases have not proven entirely satisfactory primarily due to the excessive formation of undesirable carbon oxides, and to the difficulty in maintaining control of the highly exothermic oxidation reaction. U.S. Pat. No. 3,395,159 provides an improved process wherein the oxidation of hydrocarbons is performed in a reactor system having fused vanadium oxide catalyst coated on the inner surface of the reactor, which system has the advantage of better temperature control and isothermal operation.
In J. Am. Chem. Soc., 62, 2312(1940) there are reported several processes for vapor phase oxidation of naphthalene to a mixture of partial oxidation products which include naphthoaquinone, phthalic anhydride, maleic anhydride and benzoic acid. The naphthalene oxidation processes are suitable for the production of phthalic anhydride, but are impractical for high yield conversion to maleic anhydride.
In practice the commercial processes for the oxidation of hydrocarbons are difficult to manage, and frequently the yield of desired product is low in comparison to the yield of carbon oxides and other oxidation by-products. The economics of maleic anhydride production by oxidation of butene or benzene is deficient in this respect.
Accordingly, it is an object of the present invention to provide a commercially feasible process for oxidation of hydrocarbons.
It is another object of this invention to provide a vapor phase process for converting C.sub.4 -hydrocarbons into maleic acid anhydride.
It is another object of this invention to provide a process for oxidizing butane or butene to maleic acid and acetic acid with high conversion efficiency and with a low yield of organic by-products.
It is another object of this invention to provide a process which can be controlled to convert butane into an oxidation product mixture which selectively is predominantly maleic acid or is predominantly acetic acid.
It is a further object of the present invention to provide a novel catalyst composition for vapor phase conversion of C.sub.4 -hydrocarbons into maleic acid and acetic acid.
Other objects and advantages shall become apparent from the following description and examples.